KROHNE OPTIFLEX 1300C EN - Manual (Page 92)

6
OPERATION
92
OPTIFLEX 1300 C
www.krohne.com 03/2014 - 4000172306 - HB OPTIFLEX 1300 R07 en
• Select Supervisor Supervisor Supervisor Supervisor and push [^ ^ ^ ^] 2.
i Type in the supervisor password, if this is necessary.
• Type in the new interface distance value 3.
i The selected signal is the interface signal.
• Push [^ ^ ^ ^] to accept your new value or push [> >>>] and [ ] (Esc) at the same time to reject it.
i The display goes back to the signal screen.
6.4.8 Thresholds and parasitic signals
General notes
The low-power electromagnetic signal from the device goes down the probe. The surface of the
process and objects in the tank make reflections. These reflections go back up the probe to the
signal converter. The signal converter converts the reflections into voltage amplitudes.
Reflections from objects in the tanks show as interference signals (parasitic signals).
How thresholds work
Thresholds let the device ignore reflections with small amplitudes and monitor changes in level
or interface. The voltage amplitude of signals depends on the distance of the reflection from the
signal converter. Because the voltage amplitude decreases as distance increases, the threshold
decreases logarithmically. The device uses largest signal that goes across the threshold.
The device uses the menu items that follow:
• Level Threshold (C.1.16) to monitor the level signal
• Level Threshold (C.1.16) and Interface Threshold (C.1.17) to monitor level and interface
signals
• Probe End Threshold (C.1.18) to monitor the probe end signal in TBF or Automatic mode. If
the device operates in TBF mode or must calculate the ε
r
of the product, there must be a good
probe end signal.
The electronics of the device amplify the signal. The amplification factor (level of Gain) depends
on the strength of the signal. There are 7 levels (1 to 7). A strong signal is given Gain 1, while a
weak signal is given Gain 7. When you fill or empty the tank, the device usually identifies the
signal. It automatically changes the Gain to monitor the position of the signal.
But the device cannot monitor the correct signal if:
• There are too many objects in the tank.
• There is an object that makes a large reflection in the tank.
INFORMATION!
If the device continues to select the parasitic signal for level or interface measurement, make
sure that there are no obstructions in the tank. If you cannot remove the obstruction, use the
snapshot function to filter the signal. For more data, refer to How to use the snapshot function to
filter parasitic signals on page 96
. If you cannot find the correct signal on the signal screen,
contact the supplier.